Now an Apache incubating project, PredictionIO is a machine-learning server with customizable templates, real-time query response, the ability to ingest data from multiple platforms and more. It integrates with other open source tools like Spark, MLlib, HBase, Spray and Elasticsearch. Operating System: Windows, Linux, macOS.

Under development since 1999, Shogun is a mature set of machine learning tools with support for Python, Octave, R, Java/Scala, Lua, C#, Ruby and other languages. It also has a free cloud service where users can try out the software. Operating System: Windows, Linux, macOS.

Originally an IBM Research project, SystemML is now a top-level Apache project. It describes itself as "an optimal workplace for machine learning using big data," and it integrates with Spark. Operating System: Windows, Linux, macOS.

Developed by the Google Brain team for internal use at Google, TensorFlow is now one of the most well-known open source machine learning platforms. Google is also making a cloud-based version of TensorFlow available for free to researchers. Operating System: Windows, Linux, macOS, Android.

Java-based WEKA offers a wide variety of machine learning algorithms that are useful for data mining. It was developed at the University of Waikato in New Zealand and is named for a New Zealnd bird known for its inquisitiveness. Operating System: Windows, Linux, macOS.

Natural Language Processing

This Java-based natural language processing software can identify the base forms of words, their parts of speech and whether they are names of companies, people, etc., as well as normalizing dates and times, marking up the structure of sentences in terms of phrases and syntactic dependencies, indicating which noun phrases refer to the same entities, identifying sentiment, extracting particular or open-class relations between entity mentions and getting quotes. It was designed for English but also supports Arabic, Chinese, French, German, and Spanish. Operating System: Windows, Linux, macOS.

Short for "Machine Learning LanguagE Toolkit," MALLET includes Java-based tools for statistical natural language processing, document classification, clustering, topic modeling, information extraction and more. It was first created in 2002 by faculty and graduate students at the University of Massachusetts Amherst and the University of Pennsylvania. Operating System: Windows, Linux.

Neural Networks

Formerly known as cnn, DyNet is a neural network library for C++ and Python that was developed primarily at Carnegie Mellon University. It is useful for creating applications for syntactic parsing, machine translation, morphological inflection and more. Operating System: Windows, Linux, macOS.

Initially created as a graduate thesis project, Neuroph is a Java-based lightweight neural network framework. It aims to be easy enough to use that beginners can get started quickly, while also providing the flexibility and tools that more advanced users need. Operating System: Windows, Linux.

OpenNN, short for "Open Neural Networks," is a C++ library for implementing neural networks. It boasts high performance and deep architecture. Commercial support is available. Operating system: Windows, Linux, macOS.

Created by Google's DeepMind team, Sonnet is a neural network library that runs on top of TensorFlow. According to its developers, it offers greater flexibility than other TensorFlow frameworks. Operating System: Linux, macOS.

Virtual Assistant

Mycroft boasts that it is "the world’s first open source assistant." It answers questions, plays audio and video, controls IoT-connected appliances and more. It has very minimal system requirements, and it can even run on a Raspberry Pi. Operating System: Windows, Linux, macOS.

Still under heavy development, Open Assistant aims to offer an open source alternative to Siri, Cortana and Google Now. Its goal is to create a completely customizable AI that can engage in conversation. Operating System: Linux.

Developed at the University of Buffalo, SNePS is a knowledge representation, reasoning and acting system. The group behind the project has used the research to create a virtual agent called Cassie. Operating System: Windows, Linux.